1. Field of the Invention
The invention relates to water-insoluble polymers which promote cell proliferation and to a process for their preparation. The invention furthermore relates to the use of the water-insoluble polymers which promote cell proliferation for the production of products having a surface which promotes cell proliferation and for the production of products having a coating, of the polymer, which promotes cell proliferation. The invention moreover relates to products having a surface which promotes cell proliferation and products having a coating, of the polymer, which promotes cell proliferation. For numerous medical applications of materials such as polymers, ceramics and metals, for example as suture materials, stems, implants or prostheses, good compatibilities with the immune and complement system and the blood must be ensured. This property, which is often called biocompatibility, includes avoidance of degradation phenomena of the materials by physiological components, such as enzymes and macrophages.
2. Description of the Prior Art
An improved biocompatibility of substitute materials employed medically can be achieved in principle by colonization with human cells. The process described in EP 0 290 642 initially requires covalent bonding of an intermediate layer of so-called copolymers onto polymer surfaces functionalized by carboxyl, amino and hydroxyl groups. The biocompatibility sought in the material is then achieved by careful, extracorporeal colonization of the intermediate layer with endothelial cells.
WO 90/02145 describes, with the same aim, a process in which acrylic acid is grafted onto fluorine-containing polymer substrates by irradiation with a 60Co source or a laser. After a series of chemical processes on the surface, controlled absorption of proteins takes place, which is followed by colonization with endothelial cells to establish the biocompatibility.
These processes are extremely time-consuming and cost-intensive and require the greatest care for a medical application, so that the endothelial cell layers applied extracorporeally are not damaged. It is furthermore not possible to allow the cell colonization and cell growth (cell proliferation) to be carried out by the body itself in vivo, since an undesirable thrombic reaction starts before the cell colonization.
Subsequent chemical modification of surfaces of polymeric materials with the known RGD sequence method (arginine-glycine-aspartic acid) is usually not uniform and/or standard. Untreated areas often remain, which are no longer available as starting points for cell colonization of the surface (G. Muller, Angewandte Chemie, 104 (1992) 341 et seq.).
From another technical field, according to U.S. Pat. No. 5,278,200, polymers which contain carboxylate and sulfonate groups in a ratio comparable to that of naturally occurring heparin are known. These polymers have anticoagulating properties with respect to platelets in the blood.
The present invention is therefore based on the object of improving cell proliferation on the surfaces of polymers. It has now been found, surprisingly, that water-insoluble polymers which contain carboxylate and sulfonate groups and are obtainable by free radical copolymerization of
one or more aliphatically unsaturated monomers containing carbox ylate groups, or the correspondingly functionalized derivatives of the monomers, as component I with
one or more aliphatically unsaturated monomers containing sulfonate groups, or the correspondingly functionalized derivatives of the monomers, as component II and
a component III which comprises an aliphatically unsaturated monomer or several aliphatically unsaturated monomers, the correspondingly functionalized derivatives being converted into carboxylate and sulfonate groups after the copolymerization, are capable of promoting cell proliferation.
The adhesion and the growth of cells is thus improved in a physiologically tolerated manner on the polymers according to the invention.
The polymers according to the invention are thus particularly suitable for the production of implants in which growth of endogenous or non-differentiated cells is desired.
The present invention therefore relates to water-insoluble polymers which promote cell proliferation, contain carboxylate and sulfonate groups and are obtainable by free radical copolymerization of
one or more aliphatically unsaturated monomers containing carbox ylate groups, or the correspondingly functionalized derivatives of the monomers, as component I with
one or more aliphatically unsaturated monomers containing sulfonate groups, or the correspondingly functionalized derivatives of the monomers, as component II and
a component III which comprises an aliphatically unsaturated monomer or several aliphatically unsaturated monomers, the correspondingly functionalized derivatives being converted into carboxylate and sulfonate groups after the copolymerization.
The present invention furthermore relates to a process for the preparation of water-insoluble polymers, which promote cell proliferation and contain carboxylate and sulfonate groups, which comprises obtaining the polymers by free radical copolymerization of one or more aliphatically unsaturated monomers containing carboxylate groups, or the correspondingly functionalized derivatives of the monomers, as component I with one or more aliphatically unsaturated monomers containing sulfonate groups, or the correspondingly functionalized derivatives of the monomers, as component II and a component III which comprises an aliphatically unsaturated monomer or several aliphatically unsaturated monomers, the correspondingly functionalized derivatives being converted into carboxylate and sulfonate groups after the copolymerization.
The present invention moreover relates to the use of the water-insoluble polymers, which promote cell proliferation and contain carboxylate and sulfonate groups, for the production of products having a surface which promotes cell proliferation, and to the use of the water-insoluble polymers, which promote cell proliferation and contain carboxylate and sulfonate groups, for the production of products having a coating, of the polymer, which promotes cell proliferation.
The present invention furthermore relates to the use of the water-insoluble polymers, which promote cell proliferation and contain carboxylate and sulfonate groups, for the production of medical articles, in particular artificial blood vessels, having a surface which promotes cell proliferation.
The present invention moreover relates to the use of the water-insoluble polymers, which promote cell proliferation and contain carboxylate and sulfonate groups, for the production of medical articles of plastics, ceramics or metals having a coating, of the polymer, which promotes cell proliferation.
The present invention furthermore relates to the use of the water-insoluble polymers, which promote cell proliferation and contain carboxylate and sulfonate groups, for the production of artificial blood vessels having a coating, of the polymer, which promotes cell proliferation.
The present invention also relates to products having a surface, which promotes cell proliferation, of water-insoluble polymers, which promote cell proliferation and contain carboxylate and sulfonate groups.
Such products according to the invention are preferably medical articles, particularly preferably artificial blood vessels.
The present invention also relates to products having a coating, which promotes cell proliferation, of water-insoluble polymers, which promote cell proliferation and contain carboxylate and sulfonate groups.
Products having a coating, of the polymer according to the invention, which promotes cell proliferation are preferably medical articles, particularly preferably medical articles of plastics, ceramics or metals. Medical articles having a coating, of the polymer according to the invention, which promotes cell proliferation are preferably artificial blood vessels.
The polymers according to the invention are prepared by copolymerization of three components. For the polymers according to the invention and for the process according to the invention, an aliphatically unsaturated monomer containing carboxylate and sulfonate groups or several aliphatically unsaturated monomers containing carboxylate and sulfonate groups or the correspondingly functionalized derivatives of the monomers can also be employed as component I.
For the polymers according to the invention and for the process according to the invention, an aliphatically unsaturated monomer containing carboxylate and sulfonate groups or several aliphatically unsaturated monomers containing carboxylate and sulfonate groups or the correspondingly functionalized derivatives of the monomers can furthermore also be employed as component II.
In a particular embodiment of the present invention, component I can be identical to component II for the polymers according to the invention and for the process according to the invention.
The aliphatically unsaturated monomers to be employed for the polymers according to the invention can contain both double bonds and triple bonds. The monomers preferably have one or two double bonds.
For the introduction of carboxylate groups into the polymers according to the invention, all polymerizable compounds of the formula 1), or mixtures thereof, which carry carboxylate groups are suitable, for example, as component 1, such as, for example
(CnH2nxe2x88x92qxe2x88x92x)(COORk)x,xe2x80x83xe2x80x831)
where
Rk=xe2x80x94(CH2xe2x80x94CH2xe2x80x94O)dxe2x80x94H, xe2x80x94(CH2xe2x80x94CH(CH3)xe2x80x94O)dxe2x80x94H
or
Rk=xe2x80x94(CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94O)dxe2x80x94H, xe2x80x94(CH2)dxe2x80x94NH3xe2x88x92e(Rm)e,
where
Rm=xe2x80x94CH3, xe2x80x94C2H5,
d=0, 1, 2, 3 or 4,
e=0, 1, 2 or 3,
n=2, 3, 4, 5 or 6,
q=0 or 2
and
x=1 or 2.
The ester groups are hydrolyzed after the polymerization and are thus present in ionic form. The aliphatically unsaturated monomers can be both straight-chain and branched.
Monomer components which can be derived from benzene, of the empirical formula
(C6H6xe2x88x92axe2x88x92bxe2x88x92c)AaBb(OH)c,
are also suitable for the preparation of the polymers according to the invention, for example as component I, in which
A=(CnH2nxe2x88x92qxe2x88x92xxe2x88x921)(COORk)x 
where
Rk=xe2x80x94(CH2xe2x80x94CH2xe2x80x94O)dxe2x80x94H, xe2x80x94(CH2xe2x80x94CH(CH3)xe2x80x94O)dxe2x80x94H
or
Rk=xe2x80x94(CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94O)dxe2x80x94H, xe2x80x94(CH2)dxe2x80x94NH3xe2x88x92e(Rm)e,
in which
Rm=xe2x80x94CH3, xe2x80x94C2H5 
a=0, 1, 2 or 3,
b=0, 1, 2 or 3,
c=0, 1, 2 or 3,
d=0, 1, 2, 3 or 4,
e=0, 1, 2 or 3,
n=2, 3, 4, 5 or 6,
q=1 or 2,
x=0, 1 or 2
and
B=xe2x80x94COOH, xe2x80x94SO3H, xe2x80x94NH2, xe2x80x94N+(CH3)3, xe2x80x94Oxe2x80x94PO3Hxe2x88x92 or xe2x80x94OSO3H
or
B=xe2x80x94Oxe2x80x94POxe2x88x922xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94N+(CH3)3.
Sulfonate groups can be introduced into the polymers according to the invention with the following compounds of the formula 2) or mixtures thereof as component II:
(CmH2mxe2x88x92sxe2x88x92y)(SO3R1)yxe2x80x83xe2x80x832)
where
R1xe2x80x94(CH2xe2x80x94CH2xe2x80x94O)dxe2x80x94H, xe2x80x94(CH2xe2x80x94CH(CH3)xe2x80x94O)dxe2x80x94H,
or
R1=xe2x80x94(CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94O)dxe2x80x94H, xe2x80x94(CH2)dxe2x80x94NH3xe2x88x92e(Rm)e,
in which
Rm=xe2x80x94CH3, xe2x80x94C2H5,
d=0, 1, 2, 3 or 4,
e=0, 1, 2 or 3,
M=0, 2, 3, 4, 5 or 6,
s=0 or 2,
and
y=1 or 2.
The ester groups are hydrolyzed after the polymerization and are thus present in ionic form. The aliphatically unsaturated monomers can be both straight-chain and branched.
Monomer components which can be derived from benzene, of the empirical formula
(C6H6xe2x88x92kxe2x88x92ixe2x88x92p)KkLi(OH)p,
can also be employed for the preparation of the polymers according to the invention, for example as component II, in which
K=(CmH2mxe2x88x92sxe2x88x92yxe2x88x921)(SO3R1)y,
in which
d=0, 1, 2, 3 or 4,
e=0, 1, 2, or 3,
i=0, 1, 2 or 3,
k=0, 1, 2 or 3,
m=0, 2, 3, 4, 5 or 6,
p=0, 1, 2 or 3,
s=0 or 2,
y=0, 1 or 2,
and
L=xe2x80x94COOH, xe2x80x94SO3H, xe2x80x94NH2, xe2x80x94N+(CH3)3, xe2x80x94Oxe2x80x94PO3Hxe2x88x92, xe2x80x94OSO3H
or
L=xe2x80x94Oxe2x80x94POxe2x88x922xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94N+(CH3)3.
The sum of the proportions of component I and component II for the polymers according to the invention and for the process according to the invention is preferably 5 to 30 mol %, particularly preferably 15 to 20 mol %.
For the polymers according to the invention and for the process according to the invention, the ratio of the carboxylate groups to sulfonate groups contained in the polymer is 3 to 10, particularly preferably 3 to 5.
The copolymerization of the above-mentioned monomers as components I and II is carried out according to the invention with one or more other aliphatically unsaturated monomers as component III.
A monomer which carries nonionic groups is preferably used as component III. These monomers include, for example, vinyl compounds, allyl compounds, acrylic compounds, olefins, dienes, unsaturated halogeno hydrocarbons and correspondingly functionalized derivatives thereof.
The polymers according to the invention can be prepared, for example, with the aid of emulsion polymerization according to the prior art (Hans-Georg Elias, Makromolekxc3xcle [Macromolecules], Hxc3xcthig and Wepf Verlag, Heidelberg, 1981, p. 603 et seq.).
For the preparation of the polymers according to the invention, components I, II and III can furthermore also be copolymerized in solution or in bulk by the known processes. (Hans-Georg Elias, Makromolekxc3xcle [Macromolecules], Hxc3xcthig and Wepf Verlag, Heidelberg, 1981, p. 602 et seq.).
The following solvents, for example, can be employed for copolymerization of components I, II and III in solution: water, acetone, methyl ethyl ketone, butanone, cyclohexanone, diethyl ether, tetrahydrofuran, dioxane, methanol, ethanol, propanol, butanol, cyclohexanol, dimethylacetamide, dimethyl sulfoxide, dimethylformamide, heptane, cyclohexane, benzene, toluene, dichloromethane, trichloromethane, ethyl acetate, propyl acetate, amyl acetate and acetonitrile,
Azonitriles, alkyl peroxides, acyl peroxides, hydroperoxides, peroxoketones, peresters and peroxocarbonates, peroxodisulfate, persulfate and all customary photoinitiators can be used, inter alia, as polymerization initiators. The polymerization can be initiated by heat or by electromagnetic radiation, such as, for example, UV light or xcex3-radiation.
If no monomers containing carboxylate and/or sulfonate groups but instead functionalized derivatives thereof, such as, for example, a carboxylic acid ester instead of a carboxylic acid, are used for the preparation of the polymers according to the invention, the functionalized derivatives must be converted into carboxylate or sulfonate groups after the polymerization. In the case of the carboxylic acid ester, this can be carried out by means of base-catalyzed hydrolysis. The derivatization of polymeric materials can be carried out by generally known processes (Hans Beyer, Lehrbuch der organischen Chemie [Textbook of organic chemistry], S. Hirzel Verlag, Stuttgart, 1988, p. 260 et seq.).
Products having a surface which promotes cell proliferation can be produced directly from the polymers according to the invention. However, the polymers according to the invention can also be applied, if appropriate as solutions in suitable solvents, as thin layers to standard polymers by application techniques such as spraying, painting, dipping, knife-coating or coating or by multilayer injection molding, coextrusion or calendering and lamination.
Fixing of the polymers according to the invention on standard polymers, which are activated if appropriate, by primer layers or intermediate layers of bifunctional compounds is furthermore possible.
Such standard polymers are, for example, PVC, polystyrene, polyurethanes, polyacrylates, polymethacrylates, polyesters, polyethers, polyether-block amides, polyamides, polycarbonates, polyolefins, silicones and polytetrafluoroethylene.
The measurement method for determination of the cell proliferation is described below.
Preparation of the cell suspension.
Human fibroblasts of the cell line ATCC CRL1696 (American Type Culture Collection, Rockville, Md., USA) are cultured in DMEM (Dulbecco""s Modified Eagles Medium) with the addition of antibiotics, L-glutamine and 10% of a fetal calf serum in culture bottles at 37xc2x0 C. under an atmosphere of 5% CO2 and 95% air. After incubation, the nutrient medium is removed and the cell lawn is treated with 0.05% trypsin/0.02% EDTA for 5 minutes. The cells are then washed with DMEM and suspended in the same nutrient medium.
Measurement of the cell proliferation.
In a 250 ml conical flask, a polymer sample 2xc3x972 cm in size is pricked onto a dissecting needle and sterilized with ethylene oxide, and 20 ml of the above-mentioned nutrient medium are added. The polymer sample is then inoculated with 105 cells from the freshly prepared cell suspension and incubated for 8 days. The polymer sample is removed and rinsed with sterile PBS buffer solution. The adenosine triphosphate is then extracted from the cells with the aid of hot Tris/EDTA solution and determined quantitatively with the bioluminescence reagent CLSII (Boehringer Mannheim GmbH, Mannheim).
Samples which were obtained by polymerization of component III of the particular polymer according to the invention and were prepared in the same manner were used as reference sample. In a control experiment, a polymer sample was rinsed immediately after inoculation with the cell suspension and the cells rinsed off were determined quantitatively by the method described above. The promotion of cell proliferation is expressed as the percentage quotient of the ATP concentration of the cells which have grown on the polymers according to the invention divided by the corresponding value of the reference sample.
The measurement results given in the following examples show that the cell proliferation increases between 60% and 110% on polymers according to the invention.
The following examples are intended to illustrate the invention in more detail. These examples are set forth by way of illustration only, and nothing therein shall be taken as a limitation upon the overall scope of the invention.